# 30 leading public sector organisations in the Essonne department

Tamtam tracks 66 public sector organisations headquartered in the Essonne department. This list ranks the 30 largest by number of employees on LinkedIn, led by École Polytechnique, LFB and CentraleSupélec. Their median headcount is 456. Half of them were founded in 2001 or later. The most common headquarters are Palaiseau (12), Gif-sur-Yvette (4) and Orsay (4).

This list features public sector organizations in the Essonne department. The companies are predominantly higher education institutions and research services, with a strong presence of organizations founded in the 18th and 19th centuries, indicating a long-standing tradition of academic and scientific excellence.

Notable organizations include École Polytechnique, a leading institution in science and technology, and CentraleSupélec, providing higher education. ONERA - The French Aerospace Lab focuses on aerospace research, while LFB develops medicinal products. TechnicAtome specializes in nuclear reactor design, and CENTRE HOSPITALIER SUD FRANCILIEN offers public healthcare. A significant cluster of these organizations, such as École Polytechnique, Télécom Paris, and ENSTA, are headquartered in Palaiseau.

🇫🇷 Essonne · 30 companies · Updated Nov 11, 2026

| # | Company | Industry | Headquarters | Employees | Founded |
|---|---|---|---|---|---|
| 1 | [École Polytechnique](https://www.tamtam.ai/c/ecole-polytechnique) (polytechnique.edu)<br>Leading French institution offering top-level research, academic programs, and innovation in science and technology with a strong emphasis on excellence and humanist traditions | Research Services | 🇫🇷 Palaiseau | 4,377 | 1794 |
| 2 | [LFB](https://www.tamtam.ai/c/lfb) (groupe-lfb.com)<br>Develops, manufactures, and markets medicinal products for serious, often rare diseases in Hemostasis, Immunology, and Intensive Care, with a focus on plasma-derived products and biotechnologies. | Pharmaceutical Manufacturing | 🇫🇷 Les Ulis | 2,733 | 1994 |
| 3 | [CentraleSupélec](https://www.tamtam.ai/c/centralesupelec) (centralesupelec.fr)<br>Provides higher education with 4,500 students across three campuses, 370 staff, 3 international schools, 5 associated labs, and partners with 176 universities and 140 companies. | Higher Education | 🇫🇷 Gif-sur-Yvette | 2,125 | 1829 |
| 4 | [ONERA - The French Aerospace Lab](https://www.tamtam.ai/c/onera-the-french-aerospace-lab) (onera.fr)<br>Researching future aerospace and defense challenges, contributing to industry competitiveness through expertise in all related disciplines and technologies. | Aviation and Aerospace Component Manufacturing | 🇫🇷 Palaiseau | 2,097 | 1946 |
| 5 | [TechnicAtome](https://www.tamtam.ai/c/technicatome) (technicatome.com)<br>Specialized in compact nuclear reactor design, construction, and maintenance for various sectors including naval propulsion, research, medicine, and energy | Defense and Space Manufacturing | 🇫🇷 Villiers-le-Bâcle | 1,467 | 1972 |
| 6 | [CENTRE HOSPITALIER SUD FRANCILIEN](https://www.tamtam.ai/c/centre-hospitalier-sud-francilien) (chsf.fr)<br>Public healthcare institution serving one million people in southern Île-de-France, providing medical services and hospital care to the community. | Hospitals and Health Care | 🇫🇷 Corbeil-Essonnes | 1,219 |  |
| 7 | [AgroParisTech](https://www.tamtam.ai/c/agroparistech) (agroparistech.fr)<br>Educates professionals in life and environmental sciences, focusing on sustainable resource management, innovation, and bioeconomy through various academic programs. | Higher Education | 🇫🇷 Palaiseau | 1,093 | 2007 |
| 8 | [Département de l'Essonne](https://www.tamtam.ai/c/departement-de-l-essonne) (essonne.fr)<br>Region with major transport links, hosting research centers, universities, competitive industries, and offering a high quality natural living environment. | Government Administration | 🇫🇷 Évry-Courcouronnes | 1,072 |  |
| 9 | [Télécom Paris](https://www.tamtam.ai/c/telecom-paris) (telecom-paris.fr)<br>A leading educational institution in ICT, offering various programs in engineering, masters, and PhD, with a focus on innovation and entrepreneurship in the digital world | Higher Education | 🇫🇷 Palaiseau | 953 | 1878 |
| 10 | [ENSTA](https://www.tamtam.ai/c/ensta) (ensta.fr)<br>Leading public institution for higher education, research, and innovation. Offers engineering cycles, master's, doctorates, and specialized master's degrees for scientific and technical excellence. | Higher Education | 🇫🇷 Palaiseau | 916 | 1741 |
| 11 | [Paris-Sud University (Paris XI)](https://www.tamtam.ai/c/paris-sud-university-paris-xi) (universite-paris-saclay.fr)<br>A prestigious research university focused on understanding the world, student success, and meeting society's needs with top student integration into the workforce | Higher Education | 🇫🇷 Orsay | 910 | 1970 |
| 12 | [ENS Paris-Saclay](https://www.tamtam.ai/c/ens-paris-saclay) (ens-paris-saclay.fr)<br>Public institution providing high-level scientific and cultural education for research, teaching, and leadership roles in various sectors. | Higher Education | 🇫🇷 Gif-sur-Yvette | 847 | 1912 |
| 13 | [SDIS 91](https://www.tamtam.ai/c/sdis-91) (sdis91.fr)<br>Public fire and rescue service with professional and volunteer firefighters, focusing on protection, risk prevention, and civil security policies. | Public Safety | 🇫🇷 Évry-Courcouronnes | 829 |  |
| 14 | [Institut Mines-Télécom (IMT)](https://www.tamtam.ai/c/institut-mines-telecom-imt) (imt.fr)<br>Leading public group of engineering and management graduate schools, higher education and research institution, with eight public and two affiliate schools. | Higher Education | 🇫🇷 Palaiseau | 474 | 2012 |
| 15 | [CEA-List](https://www.tamtam.ai/c/cea-list) (cea.fr)<br>A research institute specializing in digital technology, supporting companies in technological development through expertise, skills, patents, and collaborative projects | Research Services | 🇫🇷 Palaiseau | 456 | 2003 |
| 16 | [Groupe hospitalier Nord-Essonne](https://www.tamtam.ai/c/groupe-hospitalier-nord-essonne) (gh-nord-essonne.fr)<br>Regional hospital network providing comprehensive medical services including emergency, maternity, pediatrics, surgery, psychiatry, and critical care with modern technical facilities. | Hospitals and Health Care | 🇫🇷 Orsay | 446 |  |
| 17 | [Ville de Massy](https://www.tamtam.ai/c/ville-de-massy) (ville-massy.fr)<br>City with dynamic living environment, excellent transport links, attracting residents and businesses, fostering multicultural community in Greater Paris area. | Government Administration | 🇫🇷 Massy | 443 |  |
| 18 | [Synchrotron SOLEIL](https://www.tamtam.ai/c/synchrotron-soleil) (synchrotron-soleil.fr)<br>Third generation synchrotron providing advanced experimental facilities for material geometry and properties research, serving diverse scientific users worldwide. | Research Services | 🇫🇷 Gif-sur-Yvette | 403 | 2001 |
| 19 | [Institut Polytechnique de Paris](https://www.tamtam.ai/c/institut-polytechnique-de-paris) (ip-paris.fr)<br>Public higher education institution combining six top French engineering schools to deliver excellent training programs and cutting-edge research. | Higher Education | 🇫🇷 Palaiseau | 370 | 2019 |
| 20 | [Laboratoire de Physique des Plasmas](https://www.tamtam.ai/c/laboratoire-de-physique-des-plasmas) (polytechnique.fr)<br>Researching space, cold, and magnetic fusion plasmas, supporting major projects like ITER, and developing plasma technologies for various applications. | Research Services | 🇫🇷 Palaiseau | 339 | 2009 |
| 21 | [Communauté Paris-Saclay](https://www.tamtam.ai/c/communaute-paris-saclay) (paris-saclay.com)<br>Intercommunal structure uniting 27 communes in Essonne, supporting nearly 300,000 residents in the Paris-Saclay area. | Government Administration | 🇫🇷 Orsay | 254 | 2016 |
| 22 | [ENSAE Paris](https://www.tamtam.ai/c/ensae-paris) (ensae.fr)<br>A leading French institution in data science, statistics, economics, finance, and actuarial science with strong links to research and industry professionals | Higher Education | 🇫🇷 Palaiseau | 237 | 1945 |
| 23 | [C2N - Centre de Nanosciences et de Nanotechnologies](https://www.tamtam.ai/c/c2n-centre-de-nanosciences-et-de-nanotechnologies) (c2n.universite-paris-saclay.fr)<br>Research in material science, nanophotonics, nanoelectronics, nanobiotechnologies, microsystems, fundamental and applied nanotechnology science. | Research Services | 🇫🇷 Palaiseau | 225 | 2016 |
| 24 | [Ville de Grigny (91)](https://www.tamtam.ai/c/ville-de-grigny-91) (grigny91.fr)<br>A dynamic city in Essonne with ambitious urban, educational, ecological, and cultural projects led by Mayor Philippe Rio, focusing on sustainable development and community well-being | Government Administration | 🇫🇷 Grigny | 219 | 2021 |
| 25 | [IUT d'Orsay](https://www.tamtam.ai/c/iut-d-orsay) (iut-orsay.universite-paris-saclay.fr)<br>Official page of the University Institute of Technology (IUT) in Orsay, part of the University of Paris-Saclay | Higher Education | 🇫🇷 Gif-sur-Yvette | 216 |  |
| 26 | [Établissement public d'aménagement Paris-Saclay](https://www.tamtam.ai/c/etablissement-public-d-amenagement-paris-saclay) (epa-paris-saclay.fr)<br>The public establishment drives development in Paris-Saclay, a hub of science, technology, innovation, and urban planning, bolstered by top-tier academic and research institutions | Architecture and Planning | 🇫🇷 Palaiseau | 175 | 2010 |
| 27 | [Yerres](https://www.tamtam.ai/c/yerres) (yerres.fr)<br>A local government entity in Yerres, France, managing administration and elected officials in the department of Essonne, Île-de-France region | Government Administration | 🇫🇷 Yerres | 166 | 1789 |
| 28 | [LISN - Laboratoire Interdisciplinaire des Sciences du Numérique](https://www.tamtam.ai/c/lisn-laboratoire-interdisciplinaire-des-sciences-du-numerique) (lisn.upsaclay.fr)<br>Researching core digital sciences and engineering, including AI, data science, human-machine interaction, language processing, and bioinformatics, with a focus on interdisciplinary approaches. | Research Services | 🇫🇷 Orsay | 163 | 2021 |
| 29 | [Ville de Brétigny-sur-Orge](https://www.tamtam.ai/c/ville-de-bretigny-sur-orge) (bretigny91.fr)<br>Official page of a town located in Brétigny-sur-Orge Promoting a balance between city and countryside while being recognized as a sustainable and innovative community 🏡🌾🌳💡 | Government Administration | 🇫🇷 Brétigny-sur-Orge | 155 |  |
| 30 | [Mairie de Verrières-le-Buisson](https://www.tamtam.ai/c/mairie-de-verrieres-le-buisson) (verrieres-le-buisson.fr)<br>Local government managing a community with rich heritage, green spaces, and a commitment to preserving and enhancing quality of life. | Government Administration | 🇫🇷 Verrières-le-Buisson | 142 |  |

## How this list is built

Every company on this list has a Tamtam company profile. The industry is the one the company gives on LinkedIn; categories such as SaaS or fintech are classified by Tamtam's AI from the company's website and LinkedIn page; and the headquarters city must match the company's own address. Companies are ranked by the number of employees on LinkedIn, and the list is refreshed every night. Classifications can be wrong, so treat the list as a starting point rather than an official ranking. Last updated Nov 11, 2026.

## More company lists in the Essonne department

- [The largest companies in the Essonne department](https://www.tamtam.ai/l/largest-companies-essonne) (1,149)
- [Companies with in-house R&D in the Essonne department](https://www.tamtam.ai/l/r-and-d-companies-essonne) (198)
- [Multinational companies in the Essonne department](https://www.tamtam.ai/l/multinational-companies-essonne) (156)
- [Manufacturers in the Essonne department](https://www.tamtam.ai/l/manufacturers-essonne) (127)
- [Hardware manufacturers in the Essonne department](https://www.tamtam.ai/l/hardware-companies-essonne) (114)
- [Distributors and wholesalers in the Essonne department](https://www.tamtam.ai/l/distributors-and-wholesalers-essonne) (76)
- [IT Services and IT Consulting companies in the Essonne department](https://www.tamtam.ai/l/it-services-and-it-consulting-companies-essonne) (70)
- [Professional services firms in the Essonne department](https://www.tamtam.ai/l/professional-services-firms-essonne) (68)
- [Aerospace and defence companies in the Essonne department](https://www.tamtam.ai/l/aerospace-and-defense-companies-essonne) (65)
- [IT services companies in the Essonne department](https://www.tamtam.ai/l/it-services-companies-essonne) (60)
- [Retail chains in the Essonne department](https://www.tamtam.ai/l/retail-chains-essonne) (59)
- [Construction companies in the Essonne department](https://www.tamtam.ai/l/construction-companies-essonne) (56)
- [Software Development companies in the Essonne department](https://www.tamtam.ai/l/software-development-companies-essonne) (51)
- [Pharmaceutical companies in the Essonne department](https://www.tamtam.ai/l/pharmaceutical-companies-essonne) (45)
- [Electronics and semiconductor companies in the Essonne department](https://www.tamtam.ai/l/electronics-companies-essonne) (44)
- [Research institutes in the Essonne department](https://www.tamtam.ai/l/research-institutes-essonne) (42)
- [Events Services companies in the Essonne department](https://www.tamtam.ai/l/events-services-companies-essonne) (41)
- [SaaS companies in the Essonne department](https://www.tamtam.ai/l/saas-companies-essonne) (41)
- [Consulting firms in the Essonne department](https://www.tamtam.ai/l/consulting-firms-essonne) (40)
- [Family-owned companies in the Essonne department](https://www.tamtam.ai/l/family-owned-companies-essonne) (38)
- [Contract manufacturers in the Essonne department](https://www.tamtam.ai/l/contract-manufacturers-essonne) (35)
- [Research Services companies in the Essonne department](https://www.tamtam.ai/l/research-services-companies-essonne) (35)
- [Critical infrastructure operators in the Essonne department](https://www.tamtam.ai/l/critical-infrastructure-operators-essonne) (32)
- [Education providers in the Essonne department](https://www.tamtam.ai/l/education-companies-essonne) (30)

## The same list elsewhere in France

- [Public sector organisations in France](https://www.tamtam.ai/l/public-sector-organisations-france) (4,006)
- [Public sector organisations in Île-de-France](https://www.tamtam.ai/l/public-sector-organisations-ile-de-france) (993)
- [Public sector organisations in Auvergne-Rhône-Alpes](https://www.tamtam.ai/l/public-sector-organisations-auvergne-rhone-alpes) (451)
- [Public sector organisations in Grand Est](https://www.tamtam.ai/l/public-sector-organisations-grand-est) (425)
- [Public sector organisations in Provence-Alpes-Côte d'Azur](https://www.tamtam.ai/l/public-sector-organisations-provence-alpes-cote-dazur) (384)
- [Public sector organisations in Occitanie](https://www.tamtam.ai/l/public-sector-organisations-occitanie) (317)
- [Public sector organisations in Nouvelle-Aquitaine](https://www.tamtam.ai/l/public-sector-organisations-nouvelle-aquitaine) (310)
- [Public sector organisations in Hauts-de-France](https://www.tamtam.ai/l/public-sector-organisations-hauts-de-france) (261)
- [Public sector organisations in Pays de la Loire](https://www.tamtam.ai/l/public-sector-organisations-pays-de-la-loire) (187)
- [Public sector organisations in the Bouches-du-Rhône department](https://www.tamtam.ai/l/public-sector-organisations-bouches-du-rhone) (183)
- [Public sector organisations in Normandy](https://www.tamtam.ai/l/public-sector-organisations-normandy) (166)
- [Public sector organisations in Brittany](https://www.tamtam.ai/l/public-sector-organisations-brittany) (165)
- [Public sector organisations in the Nord department](https://www.tamtam.ai/l/public-sector-organisations-nord) (135)
- [Public sector organisations in Bourgogne-Franche-Comté](https://www.tamtam.ai/l/public-sector-organisations-bourgogne-franche-comte) (130)
- [Public sector organisations in Centre-Val de Loire](https://www.tamtam.ai/l/public-sector-organisations-centre-val-de-loire) (121)
- [Public sector organisations in the Rhône department](https://www.tamtam.ai/l/public-sector-organisations-rhone) (120)
- [Public sector organisations in the Haute-Garonne department](https://www.tamtam.ai/l/public-sector-organisations-haute-garonne) (111)
- [Public sector organisations in the Gironde department](https://www.tamtam.ai/l/public-sector-organisations-gironde) (109)
- [Public sector organisations in the Hauts-de-Seine department](https://www.tamtam.ai/l/public-sector-organisations-hauts-de-seine) (96)
- [Public sector organisations in the Seine-Saint-Denis department](https://www.tamtam.ai/l/public-sector-organisations-seine-saint-denis) (91)
- [Public sector organisations in the Loire-Atlantique department](https://www.tamtam.ai/l/public-sector-organisations-loire-atlantique) (82)
- [Public sector organisations in Paris](https://www.tamtam.ai/l/public-sector-organisations-paris) (460)
- [Public sector organisations in Marseille](https://www.tamtam.ai/l/public-sector-organisations-marseille) (103)
- [Public sector organisations in Toulouse](https://www.tamtam.ai/l/public-sector-organisations-toulouse) (83)

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Source: https://www.tamtam.ai/l/public-sector-organisations-essonne